This invention relates in general to humidity sensing and control devices and in particular to a humidity sensor and fan control device which continuously senses the humidity level in a room and calculates an average humidity value in the room over time, where the device senses when the current humidity level in the room has reached or exceeded a first threshold value higher than the calculated average value and turns on an exhaust fan in the room to lower the humidity level therein, and where the device senses when the current humidity level in the room has reached or decreased below a second threshold value lower than the first threshold value and turns off the exhaust fan.
In a bathroom, it is known that the humidity can rise to uncomfortable levels, particularly when hot water is being used for a shower, bath or other reasons. The moisture can cause mold and mildew to form, which is a major concern. Bathrooms typically have an exhaust fan that helps to remove the moisture to the outside and make the bathroom less humid and more comfortable. However, the exhaust fan is generally turned on by a person using a manual switch, which causes the exhaust fan to be on longer than required for some times and shorter than required for other times. That is, there is generally little or no correlation between the humidity level in the room and the amount of time that the exhaust fan is operational.
Also known are wall-mounted exhaust fan control switches where a user can manually select a numerical humidity value at which the bathroom exhaust fan will turn on when the humidity level exceeds the selected value and will turn off when the humidity level drops below the selected value. Drawbacks with these switches include the fact that the humidity levels outdoors and thus also within rooms of a home change significantly throughout the year, more so in some parts of the country than others, and these switches have no means for automatically recognizing and compensating for these different humidity levels. Also, there are some environments (e.g., dressing rooms in health clubs, public restrooms in restaurants) where it is undesirable to have the humidity level switch setting constantly being changed by people in the room.
Further, it is known to have a bathroom ceiling exhaust fan with a built-in humidity sensor that detects increases in humidity in the bathroom brought about by use of the bath or shower and automatically turns on the exhaust fan. However, this type of device is problematic in that it shuts off the exhaust fan only after a certain period of time and not as a function of the humidity level in the room, which may not allow for adequate removal of undesirable moisture in the room. Also, this type of device does not provide for manual turn-on of the exhaust fan, particularly when the device is not automatically controlling operation of the exhaust fan. Further, such exhaust fans with built-in humidity sensors tend to be relatively expensive.
What is needed is a humidity sensor and fan control device that is relatively inexpensive and easy to install and operate, and which continuously senses the humidity level in a room and calculates an average humidity value in the room over time, that automatically determines when the current sensed humidity level in a room has increased to a certain value with respect to the calculated average value and turns on an exhaust fan in the room to lower the humidity level, that automatically determines when the current sensed humidity level in the room has decreased to a certain value with respect to the calculated average value and turns off the exhaust fan, that also provides for a manual turn-on of the exhaust fan when the device is not automatically controlling operation of the exhaust fan, and that by controlling the exhaust fan in this manner mold and mildew in the room is reduced or eliminated.